As far as I am concerned, the "version" in the PM does not correspond to the revision number in your version control. The VERSION of a module should correspond to a release process of some sort that, so it seems to me that you'd want to only update that once you go from a bleeding edge version (or bug fixing branch) to some sort of actual release.

That said you could create a simple wrapper around whatever your commit command is that looks at file defining the module version, reads it, then automatically increments it in some predetermined way. In general, though, it is a bad idea for the commit process of your version control to modify the code in a non-obvious way - no matter what version control you are using.